A conventional residential staircase includes horizontal step treads and vertical risers extending vertically between the treads.
Renovating an old residential staircase is conventionally done in one of two ways:                (1) the old staircase is removed, and a new staircase constructed in place, or        (2) new treads are placed over the existing treads.        
Option (1) is expensive, and requires skilled labor familiar with staircase construction.
Option (2) often results in a staircase that does not comply with building codes. The new tread alters the rise/run or the tread depth of the staircase such that the modified staircase is no longer in code compliance.
Most staircases are built with stairs in which the tread overhangs the riser at the front of the tread. The overhang is typically between three-quarters of an inch and one and one-half inches in residential construction. Often the overhanging portion of the tread is cut off when installing new tread over the existing tread, adding to labor cost and requiring cleanup of sawdust and cuttings.
Known methods of refacing a residential staircase have other disadvantages.
Jung, U.S. Pat. No. 6,960,272 discloses a method wherein a replacement tread is placed on and overhangs the old tread. A replacement riser fits in a bottom groove formed in the overhanging portion of the replacement tread and then bends back to be supported against the old riser and against the bottom of the next lower old tread. The construction is relatively expensive and so is not practical for refacing. Fasteners installed from the upper side of the replacement tread are visible.
Abdollahi, U.S. Pat. No. 6,115,975 discloses a stair system that might be adaptable to refacing an existing staircase. The vertically spaced ends of a replacement riser is captured in grooves or dadoes formed in the upper replacement tread and a lower back molding supported on the lower replacement tread. The construction is relatively complicated and so is not practical for refacing. The back molding is visible, impairing the smooth transition between the lower replacement tread and the replacement riser.
Lopez, US Patent Application Publication 20080271390 discloses an apparatus for refacing an existing staircase. The apparatus includes a replacement tread, a nosing on the front end of the replacement tread, and a replacement riser attached to the nosing and extending from the bottom side of the replacement tread near the front end of the tread. The replacement riser is spaced a fixed distance from the front end of the replacement tread, which may change the tread depth of the stairs after refacing. The change in tread depth may cause the refaced stairs to go out of code. Having the replacement tread and replacement riser formed as an integral piece also makes the apparatus bulky to transport and handle. Installation on uneven floors can be difficult.
Defahr et al., US Patent Application Publication 20070028534 discloses a stair system that might be adaptable to refacing an existing staircase. A replacement tread plate has a nosing member faces and covers the front edge of an existing tread. A replacement riser is attached to and bears directly against the original riser below the original tread. The replacement riser extends between the top of the next lower replacement tread and the bottom of the existing tread. Defahr et al. however, does not recognize that placing the replacement riser against the original riser affects the resulting rise/run of the refaced staircase.
Thus there is a need for an improved method of renovating or refacing a staircase to avoid the disadvantages of the prior art methods.